This invention relates to a retarder brake automatic control system for dump trucks.
Speed control of dump trucks for use, for example, in ore transportation at mines is performed by manual operation of the retarder control lever by the operator during the descent of sloped roads. Effectiveness of the retarder brake largely depends on change in the road slope, weight of the load, and other factors, and the retarder brake control is performed according to the operator's judgment in each case. Accordingly, performing optimum control according to the road and load conditions is difficult, and there is a possibility of the brake disc being broken due to overheat when the descending distance is long.
In order to overcome these problems, it is known to detect the cooling oil temperature of the brake and to make the operator aware of the danger typically by alarming whenever the oil temperature has exceeded the alarming range. The operator stops the vehicle according to this alarm, and waits until the oil temperature falls to a safety level.
However, since the conventional alarm devices do not prevent brake seizure due to the heat generated and corrective action is taken only after oil temperature build-up, there is a possibility of damaging the brake. Moreover, when the operator continues to run the vehicle neglecting the alarm, the alarm unit can produce no effect. As a result, the brake is unduly used and an accident might occur. In addition, stopping the vehicle each time the oil temperature rises lowers work efficiency. Furthermore, since the operator should operate the retarder control lever together with the steering wheel, there is a problem in terms of safety and operatability.